Antimicrobial activity among multidrug-resistant Streptococcus pneumoniae isolated in the United States, 2001-2005.
Infections caused by multidrug-resistant (MDR) Streptococcus pneumoniae remain a major concern when selecting an appropriate antimicrobial agent. In this analysis, 27 781 isolates of S pneumoniae collected from 2001 to 2005 in the United States were tested for MDR phenotypes. About 25% of all isolates were MDR, defined as resistant to 2 or more of the following agents: cefuroxime, a macrolide, penicillin, tetracycline (if available), and trimethoprim-sulfamethoxazole (TMP-SMX). There was a slight decreasing trend over time in multidrug resistance prevalence with erythromycin. Among MDR strains, the most common coresistance pair was erythromycin and TMP-SMX (74% of isolates, irrespective of resistance to other agents), although penicillin-erythromycin and penicillin-TMP-SMX coresistance patterns were also found in more than 56% of MDR strains. Resistance to 4 antimicrobial agents tested was observed in 33% of all antimicrobial-resistant isolates. Levofloxacin, which was used as a representative of the fluoroquinolone class, was active against at least 98% of all MDR isolates, and the minimum inhibitory concentration (90%) (MIC(90)) for this population was 1 microg/mL (identical to the total S pneumoniae, population). Multidrug-resistant isolates from 2003 to 2005 were found to be equally susceptible (98%) to other respiratory fluoroquinolones (gatifloxacin and moxifloxacin; data not shown), although only 88% of MDR isolates (from 2001-2005) were susceptible to ciprofloxacin. Careful monitoring of multidrug resistance patterns will help guide appropriate therapeutic selection and may provide early detection of changes in resistance to more potent agents.
Thornsberry
Clyde
C
Eurofins Medinet, Inc., Herndon, VA 20171, USA.
Brown
Nina P
NP
Draghi
Deborah C
DC
Evangelista
Alan T
AT
Yee
Y Cheung
YC
Sahm
Daniel F
DF
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D011159:Population Surveillance; D012141:Respiratory Tract Infections / Q000453:epidemiology / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000302:isolation & purification; D014481:United States / Q000453:epidemiology
D000900:Anti-Bacterial Agents